Production of hydrocarbons used as fuel or base oil components and chemicals from biomass are of increasing interests since they are produced from a sustainable source of organic compounds.
The ketoacid Levulinic acid (LA, 4-oxopentanoic acid) is one of many platform molecules that may be derived from biomass. It may be produced from both pentoses and hexoses of lignocellulosic material (see FIG. 1) at relatively low cost. Levulinic acid as a platform molecule is considered to be a reactive molecule due to both its keto and acid functionality.
Esters of levulinic acid have been suggested as fuel components as well as cold flow additives in diesel fuels, and for example, the methyl and ethyl esters have been used as additives in diesel fuel. Gamma-valerolactone (GVL), which may be obtained by reduction of levulinic acid, has been used as a fuel additive in gasoline. Further reduction of GVL to 2-methyltetrahydrofuran (MTHF) provides a product that may be blended with gasoline of up to 60%. Alkyl valerates produced from levulinic acid have also been suggested as biofuels.
Levulinic acid has also been used for the production of liquid hydrocarbon fuels by a number of catalytic routes, including a method of producing a distribution of alkenes, the distribution centered around C12, involving converting aqueous GVL in a first reactor system to butenes followed by oligomerization in a second reactor over an acidic catalyst (e.g. Amberlyst® 70).
Serrano-Ruiz et al. (Appl. Catal., B, 2010, 100, 184) produced a C9-ketone (5-nonanone) by reducing levulinic acid to GVL over a Ru/C catalyst in one reactor followed by reacting 40 wt % GVL in water and 0.02 M H2SO4 in a Pd/Nb2O5+ceria-zirconia double bed arrangement at 325-425° C., 14 bar, WHSV=0.8-0.5 h−1 in another reactor. Using multiple reactors can offer more control over the process compared to using a single reactor. However, multiple reactors increase the number of process steps, which increases the capital expenditure of the process.
US Patent Publication No. 2006/0135793 A1 (to Blessing and Petrus) discloses dimerization of levulinic acid to a C10 unit in the presence of hydrogen, with a strong acidic heterogenous catalyst, e.g., ion exchange resin catalyst, having a hydrogenating metal, at a temperature in the range from 60 to 170° C. and a pressure of 1 to 200 bar (absolute). The example indicates as main products levulinic acid dimers (26%) and unreacted levulinic acid (70%). Relatively low reaction temperatures can be preferred due to the thermal instability of ion exchange resins at temperatures of above 150° C.